Florida avocado growers fear spread of exotic Asian beetle

MIAMI — This year's avocado season is making farmers happy: The 920,000-bushel crop, grown mostly in southern Miami-Dade County, is fetching prices that are almost 50 percent better than a few years ago.

But as the season comes to a close, those in the Florida avocado industry are casting a wary eye to Martin County, where the redbay ambrosia beetle continues its march southward.

Growers, scientists, and the local, state and federal governments are in a race against the beetle as it makes its way south to the $30 million avocado industry.

The beetle, believed to be a native of Asia, is described by scientists as smaller than Lincoln's nose on the penny. But it carries a fungus that has proved lethal to many trees in the laurel family, including redbays and avocados, from the Carolinas through Georgia, and now Florida. There is no method to cure the disease.

After citrus, avocados are Florida's largest tropical-fruit industry. This year's crop was more than 50 million pounds, virtually all of that grown on 7,500 acres in Miami-Dade.

``The avocado industry is very concentrated in one area,'' said Craig Wheeling, president of Brooks Tropical in Homestead, one of the largest growers, packers and shippers of Florida avocados. ``It's kind of an all-or-nothing fight down here.''

Wheeling said his best avocados were getting about $16 a bushel -- 45 percent better than the $11-a-bushel prices three years ago. He attributed the higher prices to not just a smaller crop, but to growing demand for Florida avocados. And he said that's what makes it even more crucial that scientists find a way to combat the beetle and the fungus-causing disease it carries.

Females carry the fungus spores in a special pouch within their mouths. When the insects bore into a healthy tree to check if it would be suitable for nesting, the tree is inoculated with fungi that cause a disease called laurel wilt. As it spreads, the tree's water system is disrupted, causing the leaves to wilt so quickly they don't even fall off.

The larvae and adult females feed off the fungus -- essentially, the beetle carries its farming system with it, said Jonathan Crane, a tropical-fruit plant specialist with the University of Florida's Institute of Food and Agriculture Sciences in Homestead.

There are dozens of varieties of beetles that have a symbiotic relationship with a fungus it carries. The one beetle/fungus combination that has proved deadly to the redbay and Florida avocado tree is a specific variety with the scientific name raffaelea lauricola. It was first detected in Georgia in 2002.

It took a few years to spread through Georgia and was first found in Florida's northern counties in 2005. On its own, the beetle can fly about 20 miles.

It has spread exponentially quicker the past two years to Central Florida, experts believe, because diseased trees have been cut down for firewood and brought south.